The present invention relates generally to electronic mail, and more particularly to reducing unwanted email by reducing the resources devoted to processing the unwanted email.
As the popularity of the Internet has increased drastically over the past few decades, communication via email has often become a large part of people's daily lives.
Unsolicited commercial email, also known as spam, has grown dramatically and has had a significant detrimental impact on computer users and networks. Spam wastes tangible resources relied upon by Internet service providers (ISPs) such as bandwidth, ISP disk space, user email storage space, networking and computer resources, etc. In some instances, spam can bring down servers.
One solution to the spam problem is the use of filtering techniques on a per message basis. Spam filters attempt to intercept spam before it reaches an end user's electronic mailbox. These filters can operate at an ISP or corporate email server (or locally, on an end user's computer) in order to filter the email before an end user sees the email. Spam filters generally use some form of syntactic or semantic filtering. For example, some filters may have a database of keywords which, if present in an email message, results in the email message being identified as spam. More sophisticated filters use rules that are heuristics used to assign a score to the mail message to be examined, with the score indicating the likelihood of the message being spam. Once a message is identified as spam, it may be deleted, stored in a separate mailbox associated with likely spam messages, or otherwise segregated.
While filtering can be effective in decreasing the amount of spam sent to an end user, the reduction in spam is often expensive. The ISP or enterprise mail system has to devote resources to process all incoming messages, including spam. In order to handle the immense and growing volume of email, ISPs and email providers typically have to continually maintain, upgrade, and purchase improved, more powerful and greater numbers of computers and networking resources.
A deficiency of current solutions to spam is that email sent from a source has to obtain a connection at the receiving ISP system before the receiving ISP system can identify email as spam. In particular, Message Transfer Agents (MTAs) typically handle the details of sending and receiving email across a network such as the Internet. By convention, the sending MTA (e.g., Unix sendmail or Microsoft Exchange) establishes a connection to the destination MTA. Once the connection is established, email is transferred across the Internet. Thus, existing ISP systems have to receive and process legitimate email as well as spam with a limited amount of resources having a limited number of connections. Because of the enormous volume of email, the limited number of connections available on an ISP's MTAs and, similarly, the limited amount of resources to handle the enormous volume, often result in a bottleneck to email transferring and processing. Specifically, legitimate email competes with spam for the valuable connections and processing resources, and, as a result, can be delayed.
Another solution to the spam problem occurs at the network source level. A “whitelist”, or list of email sources that are known not to deliver large amounts of spam (i.e., “trusted” sources) is created. If email is received at a router from a network source that is not on a whitelist, then email from that source is blocked at the router. The problem is that this can exclude legitimate email that happens not to pass through one of the trusted sources.
Thus, spam represents a drain on the efficiency and profitability of ISPs and email providers alike.